Be sure to attempt this mission pretty much as soon as you get it or risk failing it completely.

Breach the Petra Nebula and enter Grissom Academy on Vetus. You discover that Cerberus is behind this and that you’ll need to reach the students before Cerberus’ troops do. Eliminate the first bunch of enemies to find Sanders and have her open the way to Orion Hall.

Assault Rifle Stability Damper - On your way into the room with the biotic shielding himself, pick up the Assault Rifle Stability Damper from the steps to the right.

Reiley Bellarmine is the first student you’ll come across. He’s encased himself in an impenetrable bubble, but speak to him to learn about his sister.

SMG Heat Sink - In the classroom you can find this Weapon Mod in a desk.

Continue past the classroom and enter the adjacent room. Destroy the generator feeding power to the shields to reduce the number of cover options for the Cerberus gang in here. Once they’re taken out, you can head around to the other side of the barricaded hallway to find a Weapon.

Head into Orion Hall to join the skirmish just in the nick of time, as some of the combat-able students try to stop Cerberus troops from advancing. To complicate things a little further, you’ll have a giant bipedal robot called an Atlas Mech to turn to scrap metal, while the besieged students need protection from mounting Cerberus pressure. Note that you cannot hijack this Atlas.

Take care of the smaller Cerberus enemies before focusing your attention on the Atlas. You’ll need some armor-piercing ammo and heavy weaponry to make the Atlas feel anything more than a tiny ding.

Afterwards, find and deactivate the Cerberus camera control located on one of the benches on the bottom floor. You’ll find it closer to the corner of the room. The next step is to find the door override, which can be found upstairs by the recuperating students. After looting the control room, access the override.

The Atrium doors, located directly below, can now be pried open. The battle ahead is about to get ugly. Centurions, turrets, and an Atlas flood the area in front of you; you can count on enemies with Shields trying to flank your team as well. Note that you cannot hijack this Atlas, but you can kill the occupant with a few Sniper Rifle shots.

Push through this thick line of defense and work your way to the other side of the Atrium by way of the vestibule on the side. Eliminate all hostiles and continue onward. Note that you can use Sabotage to turn the Turrets to your side. Make sure you find and eliminate the Combat Engineers before anything else, since they will fix Turrets and Shields.

Medkit - Between the halves of the atrium on the bottom floor you can pick up a much-needed Medkit.

Laptop (Credits) - This is near the Medkit on a bench.

You soon meet up with Octavia and another student who don’t readily believe you’re on their side. A Paragon or Renegade choice will determine how you will convince them otherwise. Alternatively, if you completed the Overlord DLC for Mass Effect 2 and chose to rescue the biotic an old friend will help you convince her.

Computer Terminal (Credits) - This is in the same hallway as Octavia.

M-96 Mattock - In the Security room (Unlocked by the Old Friend mentioned above)

Sniper Rifle Piercing Mod - In the Security room (Unlocked by the Old Friend mentioned above)